Bicentric direct vent terminal

ABSTRACT

A combined air intake and combustion gas vent terminal is provided for engagement with at least one of a pair of pipes extending horizontally and being spaced apart to accommodate the inward flow of combustion air and the outwardly flow of exhaust air from a furnace. The terminal assembly is installed entirely outside of the building and has a stepped structure for engaging the pipes such that it can accommodate different sized pipes.

FIELD OF THE INVENTION

This invention relates generally to furnaces and, more particularly, toa horizontal combined air intake and combustion gas vent terminalassembly.

BACKGROUND OF THE INVENTION

Combined air intake and combustion gas vent terminals, sometimesreferred to as vent/intake terminals, have long been used with fuelfired heating appliances, particularly with side wall vented gasfireplaces and furnaces. Combined vent/intake terminals typicallycomprise concentrically mounted vent and intake conduits, with a largeintake conduit disposed around a smaller vent conduit. The terminal isinstalled in an exterior wall of a building, with the intake and ventopening exterior to the building. The recent popularity of the side wallvented furnaces, also known as horizontally vented or direct ventedfurnaces is due to the ease with which the required air intake and theflue systems may be installed in the building. Correspondingly, therehas been an increased demand for vent/intake terminals because suchdevices simplify installation effort and cost, as only a single fixtureneed be installed.

One problem commonly encountered with vent/intake terminals is anunwanted recirculation of combustion gases into the terminal intakewhich reduces the efficiency of combustion in the fuel fired appliance.Such recirculation is principally caused by the close proximity of theintake and vent openings, and one approach to solving this is the use ofan anti-mixing baffle to isolate the two.

Another problem that can occur with such systems is that of wind inducedpressure effects on the operation of the terminal. That is, thedifferent orientations of the intake and vent openings in the prior artterminals may result in wind induced pressure differentials between theopenings. This is undesirable because it modifies the pressuredifferential generated by the appliance between the intake and ventopenings. The combustion pressure differential, which causes intake airto be induced into the appliance and combustion gas to be expelledtherefrom, is carefully balanced in high efficiency furnaces to permitan efficient combustion of fuel in the appliance.

To complicate matters, the preferred combustion pressure differentialvaries with the type of system involved. For example, with oil firedfurnaces, referred to as positive pressure furnaces, it is relativelysmall as compared with that of a draft induced furnace, wherein thespeed and pressure at which the draft inducer fan operates reduces thesensitivity of the vent/intake system to wind induced pressure andbalance across the intake and vent outlet.

Another problem which can occur with concentric vent/intake terminals isthat of over-cooling of the exhaust gas. That is, during conditions ofprolonged extreme cold weather, the air intake pipe can cool the exhaustgas to an extent that frost can build up on the inner wall of theexhaust pipe near the outlet, eventually shutting down the furnace.

Another problem that the applicants have encountered with the prior artvent/intake terminals is that they may be of too great a length for aparticular installation. That is, when the vent pipes run perpendicularto the floor joists, which are typically spaced 16 inches apart, thenthe vent/intake terminal cannot be installed if it is substantiallygreater than 16 inches in length.

What is needed is a vent/intake terminal that overcomes these problemsand is easy to install and effective in use.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, the vent and intaketerminals are separated and placed in side-by-side relationship ratherthan in a concentric relationship.

In accordance with another aspect of the invention, the two pipesleading to and from the furnace extend through the wall to the outside,and the entire terminal assembly is disposed outside.

In accordance with another aspect of the invention, a stepped structuremay be provided on the inner diameters of the vent/intake terminals soas to thereby accommodate different size pipes.

In the drawings as hereinafter described, a preferred embodiment andmodified embodiments are depicted; however, various other modificationsand alternate constructions can be made thereto without departing fromthe spirit and scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a vent/intake terminal inaccordance with the prior art.

FIG. 2 is a schematic illustration of a vent/intake terminal inaccordance with one embodiment of the invention.

FIG. 3 is a front perspective view thereof.

FIG. 4 is an alternative embodiment thereof.

FIG. 5 is another alternative embodiment thereof.

FIG. 6 is a further alternative embodiment thereof.

FIGS. 7A and 7B are front and rear perspective views thereof.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is shown a vent/intake terminal assembly asinstalled in a building for use with a furnace 12 in accordance with theprior art. The vent exhaust pipe 13 is fluidly connected to the furnace12 for the purpose of conducting the flow of combustion products outsideof the building. Similarly, a combustion air pipe 14 is fluidlyinterconnected to the furnace for the purpose of conducting the flow ofoutside air to the furnace for use in the combustion process.

As part of the assembly, a coaxial pipe 16 is connected to both the ventexhaust pipe 13 and the combustion air pipe 14 as shown, with the ventexhaust pipe 13 fluidly communicating with the ambient air by way of aninner pipe 17, and the combustion air pipe fluidly communicating withambient by way of an outer pipe 18. The coaxial pipe 16 passes throughthe building outer wall 19 and extends outwardly thereof as shown. Avent cap 21 is disposed on the end of the coaxial pipe 16 and acts tophysically separate the inflow of fresh air from the outflow ofcombustion gases. That is, the combustion gases are discharged out theterminal end 22 while the ambient air flows in through the stand-offs 23and is then routed into the concentric channel formed between the innerpipe 17 and the outer pipe 18.

As mentioned hereinabove, one problem with the present approach is thatthe exhaust gases can be over-cooled by the heat exchange relationshipwith the inflow of fresh air, such that the frost can build up on theinner wall of the exhaust pipe near the outlet, thereby shutting downthe furnace. Another problem associated with this design is therelatively large length of the assembly which includes the coaxial pipe16. This overall length can be a problem in certain types ofinstallations such as those in which the joists extend transversely tothe direction of the assembly.

Referring now to FIGS. 2 and 3, a vent/intake terminal is shown at 24 inaccordance with an embodiment of the present invention. The terminalassembly 24 is installed on the outer side of a house wall 26 having acombustion air pipe 27 and a vent exhaust pipe 28 extending therethroughas shown. The centerline to centerline spacing is preferably about fourinches and the pipes 27 and 28 are standard 3 inch pipes.

The terminal assembly 24 is a unitary member having an outer end 29extending away from the wall 26 and an inner end 31 spaced from the wall26 as shown. Associated with the outer end 29 is a discharge structure32 which is cylindrical in form and comprised of three seriallyconnected portions 33, 34 and 36 that define an opening 37 therethrough.The portion 33 is of the smallest diameter and is associated with theouter end 29. The portion 34 is of a large diameter and the portion 36is the greatest diameter and is sized such that its inner diameterallows a close fitting over the vent exhaust pipe 28 as shown. Thisarrangement allows for the discharge of exhaust gases from the ventexhaust pipe 28 through the discharge structure 32 as shown by the boldarrows.

Connected to the discharge structure 32, at a point between portions 33and 34, is a wall 38 which extends at an oblique angle toward the innerend 31. Near the inner end of the wall 38 is an integrally connectedaxially extending portion 39 which terminates at the inner end 31. Thewall 38 and the axially extending portion 39, together with the portions34, 36 and the outer surface of the vent exhaust pipe 28 define aninternal space 41 for the flow of ambient air therethrough and into thecombustion air pipe 27 as shown by the lighter weight arrows. A standoffstructure 42 may be provided to interconnect the wall 38 and a surfaceof the combustion air pipe 27 as shown. This structure may or may not bein direct contact with the house wall 26. As will be seen, the standoffstructure 42 allows for the flow of ambient air around that structureand into the internal space 41.

It should be recognized that the two pipes 27 and 28 are necessarilyspaced and may be spaced either vertically or horizontally.

A modified embodiment of the present invention is shown in FIG. 4wherein the discharge structure 43 does not include an outwardlyextending portion but rather has three inwardly extending portions 44,46 and 47. Its internal diameter is stepped to accommodate the possibleuse of different sized vent exhaust pipes 28. That is, the assembly maybe installed with the portion 47 engaging the outer diameter of the ventexhaust pipe 28 as shown or, the smaller and longer extending ventexhaust pipe may be made to engage the inner surface 48 of the portion46 as shown by the dotted lines.

It will also be seen in the FIG. 4 embodiment that there is no standoffinstalled in the axially extending portion 39. That is, the entireassembly is installed on, and supported by, the vent exhaust pipe 28.

Another embodiment is shown in FIG. 5 wherein a discharge structure 49includes only an outwardly extending cylindrical portion 51 as shown,with the vent exhaust pipe 28 engaging the inner diameter thereof.Further, the wall 52 includes a radially extending portion 53, anobliquely extending portion 54 and an axially extending portion 56.Again, no standoffs structure is provided, and the entire assembly isagain supported by the vent exhaust pipe 28.

The FIG. 6 embodiment has a discharge structure 32 identical to that asshown in FIG. 2 but the wall 52 is identical to that of the FIG. 5embodiment and includes the radially extending portion 53, the obliquelyextending portion 54 and the axially extending portion 56. FIGS. 7A and7B are respective front and rear perspective views thereof, with astandoff structure 57 being included.

As will be seen, each of the above designs are for a unitary ventstructure that is installed entirely outside of the building, isattached and supported by one or more pipes extending outwardly from thebuilding and allows for the independent discharge of combustion gasesand the inflow of combustion air through parallel pipes extending fromthe house. Because of its outside disposition, it can accommodate anyinternal structure of a home without installation problems, and becauseof the parallel relationship, the exhaust gases remain uncooled untilthey leave the terminal.

1. A horizontal combined air intake and combustion gas vent terminalassembly for registration with a pair of spaced pipes extendinghorizontally outwardly through a wall comprising: a shell having anouter end and an inner end, said outer end having an opening formedtherein, with said opening being defined by a discharge structure thatengagingly registers with one of said pair of spaced pipes; and a wallattached to said discharge structure and extending generally radiallyoutwardly therefrom and terminating at said inner end, said walldefining an internal space which fluidly interconnects an opening in theother of said pair of spaced pipes with the ambient air which flowsinwardly around said inner end.
 2. A gas vent terminal assembly as setforth in claim 1 wherein said pair of spaced pipes are verticallyspaced.
 3. A gas vent terminal assembly as set forth in claim 1 whereinsaid pair of spaced pipes are horizontally spaced.
 4. A gas ventterminal assembly as set forth in claim 1 wherein said discharge endopening is cylindrical in form with a horizontally extending axis.
 5. Agas vent terminal assembly as set forth in claim 1 wherein saiddischarge structure is cylindrical in form with its axis horizontallyaligned.
 6. A gas vent terminal assembly as set forth in claim 1 whereinat least a portion of said wall comprises an obliquely extendingportion.
 7. A gas vent terminal assembly as set forth in claim 1 whereinsaid spaced pipes extend through the wall and wherein said gas ventterminal assembly is disposed entirely outside of said wall.
 8. A gasvent terminal assembly as set forth in claim 1 and including anengagement structure disposed on the inner side of said wall to engageand register with said other of said pair of spaced pipes.
 9. A gas ventterminal assembly as set forth in claim 8 wherein said wall is steppedso as to accommodate different sized pipes.
 10. A gas vent terminalassembly as set forth in claim 1 wherein said discharge structure isstepped so as to accommodate different sized pipes.
 11. A gas ventterminal assembly as set forth in claim 1 wherein the terminal assemblyis unitary in structure and composed of a plastic material.
 12. A gasvent terminal assembly as set forth in claim 1 wherein said pair ofspaced pipes are spaced at a distance of about four inches betweencenterlines.